I had worked on a similar project where website got penalized just due to the news/articles update on the front page ( ie the main landing page)
The rankings of your site has indeed dropped to pages 500 for your targeted keywords, although it would be too early to label it as penalty ( it could be on its way to temporary/or permanent penalty). Some of the issues which I found are as given below :-
Issue 1) The content of your site is being published on other sites as well which could be confusing google. Google starts to act like a fickle-minded child who can throw weird tantrums at anything if it doesnt like anything in particular. Over the past few years Google is getting more and more strict in terms of Content.
Even if you have genuinely published unique articles, press releases,your ranking power can get sucked by external sites if they publish your article and get crawled first (ie labelled UNIQUE by Google).
For some of your articles/news, Google has granted ranking powers to
Clickfire Webmaster News - Hosting, Domains, Web Development +
Aplus.Net Tops List of Web Hosting Companies and several other websites where your articles are getting published and crawled even before they get crawled on your site.
This could be a major reason behind this trouble.
Issue 2) (Minor)Titles are too long (News/Article Posts), which could dilute the concentration of targeted keyword and its associated ranking.
SOLUTIONS
You can try to switch off NEWS/ARTICLES temporarily for 1-2 months. Make sure that any new article news get crawled on your site first and then on any other website. Few months back my main site received duplicate penalty where some competitors were using this trick to bring down ranking power of our published articles
. We deleted our own original articles and site jumped back to life again
If this was the only issue, then Google will surely roll-back the previous rankings for your website.
Since you must be well aware of
SEO, I am sure you must haven't implied any of the techniques listed at
Avoid these SEO Techniques SEO HAWK ( My little link promotion
)
( If your Site retains its previous rankings, then I would hope you will give me some advertising space at Discounted Rates
)